1. Field of the Invention
The present invention generally relates to chemically amplified resist compositions, and more particularly, to photosensitive polymers containing silicon and to resist compositions containing such polymers.
2. Description of the Related Art
As the integration density and complexity of semiconductor devices continue to increase, the ability to form ultra-fine patterns becomes more and more critical. For example, in 1-Gigabit or higher semiconductor devices, a pattern size having a design rule of 0.2 xcexcm or less is needed. For this reason, in lithography processes, lower wavelength devices such as the ArF eximer laser (193 nm) have emerged as exposure light sources which are preferred over the more conventional and higher wavelength KrF eximer laser (248 nm).
However, compared with conventional (KrF) resist materials, resist materials which are suitable for use with the ArF eximer laser suffer from a variety drawbacks. One significant problem relates to the increased occurrence of collapsed patterns as the aspect ratio of pattern features is increased. As a result, patterns must generally be formed using resist layers of 4000 xc3x85 or less in thickness. Other problems result from the inferior transmittance of conventional ArF resists relative to that of KrF resists. For example, the low transmittance is another limiting factor on the thickness of the ArF resist layer.
In addition, the resistance to dry etching of almost all well-known ArF resists is at best on par with, an in most cases inferior to, that of KrF resists. This makes it difficult to achieve a satisfactory profile when patterning an underlying layer is by lithography.
In an effort to overcome these problems with convention ArF resists, a bi-layer resist (BLR) technique has been suggested in which lithography is performed using a resist material containing silicon. Using this technique, silicon atoms within the resist material are glassed in the form of SiOx during dry etching by O2 plasma to form a curing layer, and the curing layer is used as an etching mask during subsequent dry etching. In this manner, the resistance to dry etching is increased. Therefore, in the case where the aspect ratio is large, the collapse of patterns is avoided and the formation of patterns is facilitated. As a result, patterns having large aspect ratios can be formed using high resolution power.
The amount of silicon contained in a polymer of the resist material is an important factor in establishing the characteristics of the BLR process. Generally, as the amount of silicon increases, thermal stability of the resist layer decreases and wettability with respect to a developing solution is reduced. Therefore, silicon must be contained with an amount suitable for a BLR process, and there is a demand for the development of a such resist material exhibiting favorable thermal stability and wettability characteristics.
It is an objective of present invention to provide a photosensitive polymer which has sufficient silicon content and which exhibits favorable lithography characteristics when used as a resist material.
It is also an objective of the present invention to provide a resist composition which has a silicon content that is sufficient for use as the BLR of ArF eximer laser lithography, and which exhibits favorable thermal stability and wettability characteristics.
According to one aspect of the present invention, there is provided a photosensitive polymer comprising a polymer of alkyl vinyl ether, represented by the following formula: 
where
R1 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH3)3,
R2 is xe2x80x94H, xe2x80x94OH, xe2x80x94OCOCH3, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH(CH3)2)3,
R3 is xe2x80x94H, xe2x80x94OH or xe2x80x94OCOCH3,
R4 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3, xe2x80x94CH2OSi(CH3)2C(CH3)3 or xe2x80x94CH2OSi(CH(CH3)2)3 and
at least one of R1, R2 and R4 is a Si-containing group.
In another aspect of the present invention, there is provided a photosensitive polymer comprising a copolymer of alkyl vinyl ether and maleic anhydride, represented by the following formula: 
where
R1 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH3)3,
R2 is xe2x80x94H, xe2x80x94OH, xe2x80x94OCOCH3, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH(CH3)2)3,
R3 is xe2x80x94H, xe2x80x94OH or xe2x80x94OCOCH3,
R4 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3, xe2x80x94CH2OSi(CH3)2C(CH3)3 or xe2x80x94CH2OSi(CH(CH3)2)3, and
at least one of R1, R2 and R4 is a Si-containing group.
According to still another aspect of the present invention, there is provided a resist composition comprising a photosensitive polymer and a photoacid generator (PAG), wherein the photosensitive polymer comprises a polymer of alkyl vinyl ether, represented by the following formula: 
where
R1 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH3)3,
R2 is xe2x80x94H, xe2x80x94OH, xe2x80x94OCOCH3, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH(CH3)2)3,
R3 is xe2x80x94H, xe2x80x94OH or xe2x80x94OCOCH3,
R4 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3, xe2x80x94CH2OSi(CH3)2C(CH3)3 or xe2x80x94CH2OSi(CH(CH3)2)3 and
at least one of R1, R2 and R4 is a Si-containing group.
According to still another aspect of the present invention, there is provided a resist composition comprising a photosensitive polymer and a photoacid generator (PAG), wherein the photosensitive polymer comprises a copolymer of alkyl vinyl ether and maleic anhydride, represented by the following formula: 
where
R1 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH3)3,
R2 is xe2x80x94H, xe2x80x94OH, xe2x80x94OCOCH3, xe2x80x94OSi(CH3)2C(CH3)3 or xe2x80x94OSi(CH(CH3)2)3,
R3 is xe2x80x94H, xe2x80x94OH or xe2x80x94OCOCH3,
R4 is xe2x80x94H, xe2x80x94OSi(CH3)2C(CH3)3, xe2x80x94CH2OSi(CH3)2C(CH3)3 or xe2x80x94CH2OSi(CH(CH3)2)3 and
at least one of R1, R2 and R4 is a Si-containing group.